1. Field
Embodiments disclosed herein relate to an ultrasound imaging apparatus configured to simultaneously obtain ultrasound elasticity information and photo-acoustic information on a subject, and a control method thereof.
2. Description of the Related Art
PAT (Photo Acoustic Tomography) is a technology suitable for imaging a tissue of a body by using a method of combing a high spatial resolution of an ultrasound image with a high optical contrast of an optical image. As a laser is radiated on a tissue of a living body, the short electromagnetic pulse of the laser is absorbed into the tissue of the body, and thus a temporary acoustic pressure is generated by the thermo-elastic expansion at a portion of the tissue that acts as the source at which the initial ultrasound wave is generated. The ultrasound waves formed as such are reached at the surface of the tissue of a body at various intervals of delays, and the imaging of such is referred to as a photo-acoustic image.
The ultrasound imaging technology is an established medical imaging technology configured to diagnose a lesion inside a human body by using an ultrasound wave. An ultrasound image is mostly displayed as a B-mode image that uses the coefficient of reflection according to the difference of the impedance between the tissues. However, for a tumor or a cancer lesion, a portion may exist having no difference in the coefficient of reflection compared to the surrounding tissues, and therefore such portions may not be distinguishable on the B-mode image. On the contrary, ultrasound elastography, which images the mechanical characteristics of a tissue, provides considerable assistance in diagnosing a lesion such as a cancer tissue. By using the characteristic that, when an outside force is applied to deform a tissue, a hard tissue such as cancer has a small displacement in the direction of the force applied, and a soft tissue has a large displacement in the direction of the force applied, a diagnosis may be made whether the lesion of the tissue is cancer, and the method as such is referred to as an ultrasound elasticity imaging method.
The ultrasound elastography method may be capable of determining the characteristic value (the stiffness) of the tissue itself. Thus, this method may be useful in the diagnosis of a tumor that is generated in a relatively uniform medium such as breast cancer or prostate cancer. Therefore, a surgical procedure, such as a biopsy that causes an inconvenience of a patient, may be reduced, and thereby the usefulness of the ultrasound elastography method may be significant.
Since the photo-acoustic imaging method and the ultrasound elasticity imaging method are capable of distinguishing a lesion tissue and a normal tissue, respectively, both methods may be used for a purpose such as an early diagnosis of cancer. If the photo-acoustic imaging method and the ultrasound elasticity imaging method are simultaneously used, the accuracy of a diagnosis may be further enhanced.
Suggested methods to simultaneously use photo-acoustic image information and ultrasound elasticity image information include a method of displaying a photo-acoustic image and an ultrasound elasticity image by obtaining each of the photo-acoustic image and the ultrasound elasticity image, and a method of matching a photo-acoustic image and an ultrasound elasticity image by obtaining each of the photo-acoustic image and the ultrasound elasticity image. However, to simultaneously use photo-acoustic image information and ultrasound elasticity image information in the above methods, each of the images is separately needed to be obtained, and thus inefficiencies result in terms of the test time and the cost of the tests, and also, an error may occur when the two images are matched.